Unsaturated aldehydes such as acrolein or trans-2-hexenal are ubiquitous pollutants that are present in large quantities in the environment. Volatile aldehydes such as acrolein are generated during incomplete combustion of fossil fuels, whereas longer chain aldehydes are natural constituents of food. Although these aldehydes display high toxicity, their cardiovascular effects are unknown. We propose that environmental aldehydes cause abnormal activation of the endothelium and platelets, thereby distorting their response to injury and the integrity of the vessel wall. These changes promote the formation of atherosclerotic lesions and enhance the risk of myocardial infarction. To test this hypothesis we will examine the processes that regulate aldehyde toxicity in platelets, and examine aldehyde-induced changes in platelet and endothelial interactions. Our Specific Aim 1 is to eluciate the metabolism of unsaturated aldehydes in the platelets. We will identify, characterize and quantify the major metabolites of acrolein and hexenal generated in platelets and assess the contdbution of glutathione-S-transferases and oxidoreductases to the overall aldehyde metabolism in these cells. Specific Aim 2 is to examine aldehyde-induced changes in platelet function. We will measure platelet activation by aldehyde, their metabolites and lipoprotein adducts and assess the adhesive capacity of aldehyde-treated platetets towards matrix proteins. In addition, we will identify and define the signalling aspects of the specific integrin receptors involved in augmented adhesion and measure platelet microparticle (MP) formation. To delineate endothelial toxicity of aldehyde exposure, in Specific Aim 3, we will examine endothelial dysfunction by measuring the expression of inducible adhesion molecules. These experiments will also test the hypothesis that due to aldehyde-induced upregulation of ICAM-1 on the endothelium, platelets become hyperactive in the presence of sub-threshold levels of agonist, and that the interaction between the platelets, MP and the endothelium is due to the binding of the fibrinogen-bound platelets to ICAM-1 or via P-selectin. To test this hypothesis, we will examine platelet and MP interactions with the endothelium of aldehyde exposed wild-type and apoE-null mice which develop atherosclerosis spontaneously. In addition, we will elucidate the changes in endothelial function using ex vivo preparations of aortic rings prepared from exposed and unexposed mice. The results of this project will lead to a better understanding of the mechanisms by which environmental aldehydes affect key mechanisms regulating vascular reactivity and coagulation pathways. This understanding may be critical for evaluating the risk of atherosclerosis, thrombosis and myocardial infarction due to aldehyde exposure and in establishing the role of these and related environmental toxicants in precipitating acute cardiovascular events.